1. Field of the Invention
The invention relates to a torque limiter, a wind turbine, and a wind turbine generator.
2. Description of the Related Art
A wind turbine generator includes pitch drive devices used to adjust the pitch angle of blades of a wind turbine and yaw drive devices used to turn a blade-supporting nacelle relative to a tower. Each of the pitch drive devices and the yaw drive devices is formed of a combination of a motor capable of rotating in the forward rotation direction and the reverse rotation direction and a speed reducer (see, for example, Japanese Patent Application Publication No. 2010-1996 (JP 2010-1996 A)). Such a wind turbine generator has a problem that, when an abrupt change occurs in the wind speed or in the wind direction, excessively high torque acts on the motors and the speed reducers of the pitch drive devices and the yaw drive devices, which may cause damages to the motors and the speed reducers.
In order to solve this problem, a torque limiter may be arranged between a driving member, such as a motor shaft of a motor, and a driven member to which power is transmitted from the motor, as described in Japanese Patent Application Publication No. 2005-147316 (JP 2005-147316 A). In the torque limiter, a plurality of wedge-shaped spaces is formed between an outer peripheral face of an inner ring and an inner peripheral face of an outer ring so as to be arranged in the circumferential direction, and rollers that are brought into wedge-engagement with the inner ring and the outer ring upon application of external force to the rollers are arranged in the wedge-shaped spaces. Due to this configuration, torque is transmitted between the inner ring and the outer ring while the rollers are in the wedge-engagement state between the inner ring and the outer ring, and when a torque equal to or higher than a predetermined magnitude is applied, the wedge-engagement of each roller is cancelled. If the wedge-engagement is cancelled, the inner ring and the outer ring rotate at idle, and thus transmission of torque between the inner ring and the outer ring is interrupted.
The torque limiter is able to interrupt the transmission of torque when the inner ring and the outer ring are rotating relative to each other in one direction. However, when the inner ring and the outer ring are rotating relative to each other in the other direction (the direction opposite to the one direction), the torque limiter is not able to interrupt the transmission of torque. Therefore, in the case where the motor is rotated in the forward rotation direction and the reverse rotation direction as in each of the aforementioned pitch drive devices and yaw drive devices, the problem that damages are given to the motor still occurs if excessively high torque is applied in the other direction.